Rewrite ${((7^{-9})(9^{-4}))^{5}}$ in the form ${7^n \times 9^m}$.
Explanation: ${ ((7^{-9})(9^{-4}))^{5} = (7^{(-9)(5)})(9^{(-4)(5)})} $ ${\hphantom{ ((7^{-9})(9^{-4}))^{5}} = 7^{-45} \times 9^{-20}} $